Two advantages of the European Union relate to science and citizenship. In science, national budgets are being seriously cut so that research--for example, into dark matter--is being sorely impacted with facilities being closed because funding has stopped. The EU has its own science research funding and therefore can buffer some of the negative affect of nations' budget cuts. Regarding citizenship, travel and work between member nations is unrestricted, so people facing economic difficulties and unemployment in their home nations may more easily move between nations to find employment.

The European Union became a much more powerful trading partner on the world stage, meaning the products of member countries were more competitive, their access to resources easier, not to mention their tourism industry experienced a boost as there is now a single currency and much easier borders to cross.

On the down side, EU members that have financial difficulties (Spain, Portugal, Italy, Greece) put a drain on the entire union, and so the tax dollars from a more successful country like Germany must be used to shore up economies outside the country lest one drag down the others.

There are benfits to such a marriage, but safe to say they are experiencing growing pains and a bit of buyer's remorse.

From a travelling tourist's point of view, it's great to be able to drive between the borders of EU countries without having to stop at checkpoints to produce passport identification. The adoption of the Euro also makes money-changing a one-time event--changing the dollar (or other home-based currency) for Euros instead of Marks, Francs, Lira, etc.

Apart from the trade benefits, it is clear that there are plenty of negatives, as is shown by the current crisis that member nations such as Ireland, Portugal and Greece are facing. In addition, the loss of sovereignty is something that is much complained about. It is very difficult to have one system of laws for so many different countries with their own culture and background. Laws obviously that may be suitable for one part of the EU may not necessarily be applicable for other parts. Lastly, trying to unite so many countries together is an administrative nightmare that complicates so many processes that were formerly very simple.

I will answer this in terms of the advantages and disadvantages of the EU for the member countries.

Membership in the EU is a mixed blessing. The greatest good, in general, is access to the free trade zone. By becoming part of the EU, any country has access to the markets of all the other countries in the EU. This is, generally speaking, an advantage because it increases the size of the potential market for each firm.

On the other hand, EU membership brings with it some limitations on sovereignty. EU members cannot enact laws that violate various provisions of the basic EU laws. For example, they cannot close their borders to people from other countries in the EU. There are countless other examples having to do with much lesser issues like the labelling of food. This means that the countries are not free to enact any sort of laws that they want, which is something that sovereign countries are supposed to be able to do.